Your ears never sleep: Auditory processing of nonwords during sleep in children

Abstract

The auditory system in humans is the only sensory system that remains active for the continuous scanning and processing of information during sleep; however, little research has investigated this phenomenon. This study examined whether a brief exposure to auditory stimuli during sleep could result in memory traces indicated by event-related potentials (ERPs) in children. Twelve preschool children with normal hearing (2–5 years) were presented with three randomly selected nonwords (250 trials; 45–50 dB SPL) for 10 min during a regular nap (sleep state verified by EEG). After the nap, children’s memory for the stimuli was evaluated using a passive listening version of the “old/new” ERP paradigm that included three nonwords from the nap exposure (repeated condition, 45 trials), 3 new nonwords (sham repeated condition, 45 trials), and 45 other distinct nonwords (novel condition). Memory for the “nap exposure” words was reflected by increased positive amplitudes at midline parietal locations between 350 and 600 ms compared to the sham and novel conditions. This evidence of the memory trace for the auditory stimuli experienced during sleep can have implications for children with hearing loss who routinely remove their assistive devices during sleep. Preliminary results from children with cochlear implants will be discussed.